Catalysts employed in hydrocarbon conversion processes become partially deactivated due to carbonaceous deposits accumulating on the catalyst surface. Various methods for regenerating the catalyst by combustion with an oxidizing gas have been developed.
U.S. Pat. No. 3,902,990 discloses a process for regenerating spent catalyst contaminated by carbonaceous deposits by contacting the spent catalyst with a hot flue gas emanating from a first dense phase regeneration zone. The heated spent catalyst is then contacted counter-currently with an oxygen-containing gas in the first dense phase regeneration zone to produce partially regenerated catalyst which is subsequently contacted concurrently with an oxygen-containing gas in a second dense phase regeneration zone.
In accordance with this process, hydrocarbons which are contained in the void spaces of spent catalysts are removed by stripping with a stripping gas in a zone located outside of the regenerator. The stripped spent catalyst then flows from the stripping zone through a conduit and into the regeneration vessel. The spent catalyst is discharged in upper regions of the vessel and flows in a downward direction and is contacted by a hot upflowing flue gas which combusts the coke and heats the catalyst. The heated catalyst then continues to flow down into the dense fluidized regeneration bed for further heating and oxidation of the carbonaceous material.
U.S. Pat. No. 3,904,548 discloses a method and system for recovering compounds deposited on catalysts in the hydrocarbon phase and effecting regeneration of catalyst particles in a swirl-type dense fluid catalyst bed regeneration operation. These objectives are accomplished by limiting the volume of regeneration gas brought in contact with the catalyst in selected vertical segments of the regeneration zone. The regeneration zone is supplied with regeneration gas in the lower portion thereof by a plurality of radiating distributing grids or segments individually controlled with respect to the volume of regenerating gas desired to be passed through any given segment.
U.S. Pat. No. 4,150,090 discloses an apparatus for regenerating spent catalyst. The apparatus incorporates a closed vessel having a centered stand pipe concentrically arranged within a spent catalyst distributor. The catalyst is carried upwardly by the distributor and is scattered evenly and concentrically about the distributor. The spent catalyst is deposited on or near the top of a dense phase catalyst bed by a plurality of radially extending catalyst distributor arms or troughs. Conduits convey a fluid such as steam to each of the radial arms to fluidize the catalyst particles and eject at least a portion of the catalyst at various points along the length of the arms, thereby providing better catalyst distribution into the dense phase catalyst bed. A symmetrically arranged air distributor system, which includes a number of transverse branches having small nozzles mounted thereon, form a grid pattern below the lower portions of the catalyst bed in the regenerator to provide air for burning the coke on the spent catalyst.
U.S. Pat. Nos. 4,353,812; 4,434,245 and 4,439,533 all disclose a process and related apparatus for regenerating and cooling hot fluidized catalysts. The spent catalysts entering the regenerator are dispersed to the dense fluid bed by being deflected off of a horizontal surface located above the catalyst inlet. The particles then flow from the dense phase fluidized bed into the shell side of a vertically oriented shell and tube heat exchanger where cooling occurs via indirect heat exchange with a cooling media circulating in the tubes. The cooled catalyst particles reenter the regenerator for further treatment before being discharged.